High temperature platens

ABSTRACT

A relatively large platen for a press is disclosed suitable for use up to temperatures of at least 2,500*F. and up to pressures of at least 3,000 per square inch. The platen includes a pressure plate made of a heat conducting ceramic having internal heaters which ceramic is backed up by a ceramic heat insulator and a heat sink, beween the heat insulator and the press, to prevent the press from increasing appreciably in temperature.

[45] Aug. 28, 1973 United States Patent [191 Heisman et al.

100/93 P X 100/93 P 100/93 P X [5 HIGH TEMPERATURE PLATENS 3,139,816 7/1964 Jemison =1 3,456,581 7 1969 2 be [75] Inventors: Robert M. HQIIIIIIII, Palos Verdes 3,463,080 811969 g g ct FOREIGN PATENTS OR APPLICATIONS Peninsula; Charles R. Chase, Long Beach; Louis A. Weisenberg, Tustin, all of Calif.

639,331 6/1950 Great Britain 219/243 [73] Assignee: North American Rockwell Corporation, El Segundo, Calif. Primary Examiner-Wayne A. Morse, Jr. Sept. 27, 1971 Assistant ExammerPhil1p R. Coe

[21] Appl. No.: 183,904

[22] Filed:

Attorney-L. Lee Humphries, Charles F. Dischler et al.

[57] ABSTRACT A relatively large platen for a press is disclosed suitable for use up to temperatures of at least 2,500'F. and up to pressures of at least 3,000 per square inch. The platen includes a pressure plate made of a heat con- [52] US. 100/93 P, 100/295, 219/243, 219/468, 425/407, 425/411 [51] Int. Cl... B30b 15/34, B30b 15/06, B30b 15/28 [58] Field of Search 100/93 P, 295; 425/384, 407, 411; 219/243, 468,548, 551

ducting ceramic having internal heaters which ceramic [56] References Cited is backed up by a ceramic heat insulator and a heat 7 UNITED STATES PATENTS sink, beween the heat'insulator and the press, to prem. w m .m y m .m c m e r. F w a m M m D m S c I .m m m & C H 8 e r P e m nm wm 100/93 P X 100/93 P X 219/243 UX 3,047,051 7/1962 Matveeff....................... 3,119,728 1/1964 Janapal..... 2,638,964 5/1953 Andma PATENTEDAUGZB I975 SHEEI 1 OF 5 FIG. I

Pmmiuwczsmn 3.7543199 sum- 2 or 5 FIG.2

PATENTED AUG 2 8 I973 SHEET U 0F 5 mm mm HIGH TEMPERATURE PLATENS FIELD OF INVENTION This invention relates to a platen and, more particularly, to a heated platen of relatively a large size, operating at a high temperature and pressure.

BACKGROUND OF THE INVENTION I The fact that metals decrease in strength as the temperatures increase is well known. Therefore, platens which operate in the range of 2,000 F. are normally made of ceramic because most ceramics do not degrade at this temperature, while under atmospheric conditions, and because ceramic platens are more readily fabricated than platens made of refractory metals. Up to now the prior art teaches that, to increase the temperature of an object or item while under pressure, the current should be conducted through the item or through a resistor surrounding the item; for example, as taught by U.S. Pat. Nos. 2,941,241, 2,941,242, 2,941,243, and 3,941,244. This method is effective when the item is relatively small, since uniformity in temperature can be readily achieved in the item. However, when the item to be heated and pressed is relatively large, for example, requiring platens about 30 by 48 inches in size, resistance heating around the item is out of the question and resistance heating through the item is impractical because current will flow in the path of least resistance. Thereby the item would be inherently non-uniform in temperature. Therefore, the heat to the item should be applied by the platens.

OBJECT OF THE INVENTION An object of this invention is to produce high temperature platens capable of being heated to about 2,000 F. and of transmitting a unit pressure of about 3,000 pounds per square inch.

Another object of this invention is to produce a ceramic platen that can be heated'to about 2,300 F. uniformly.

Another object of this invention is to produce an efficient ceramic platen with electrical resistance heaters embedded therein.

Another object of this invention is to produce for a press a heated ceramic platen that is relatively a good heat conductor with a ceramic heat insulator between the heated ceramic and the press ram.

Another object of this invention is to provide a ceramic platen with internal ceramic resistance heaters so that the platen is substantially uniformly heated and has relatively long operating life.

These and other objects and features of the invention will become more apparent after studying the following description of the preferred embodiment of the invention together with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS- FIG. 1 shows pictorially a typical press on which the novel platens are installed;

FIG. 2 is a pictoral view with a corner broken away of one of the novel platens removed from the press shown in FIG. 1;

FIG. 3 is an exploded pictorial representation of the novel platen; 1

FIG. 4 is an enlarged cross section elevation of the novel platen;

FIG. 5 shows, schematically, a typical use for the novel platen.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, a standard 1,000 ton hydraulic press is shown. A press of this size is required to develop the necessary 3,000 psi in an area up to 4 square feet. However, if a larger area is to be covered by a unit pressure of this size, a larger capacity press should be used. Conversely, if a smaller area is to be covered by the same size unit pressure, a smaller capacity press could be used. Then, if the working area becomes extremely small, platens of the prior art teachings may be more advantageous to use in the process. The novel platen described and taught herein can be made any size by using the well known modular construction techniques. The press includes a stationary bed 10 and a plurality-of upright posts 11, for example, four which supports a hydraulic piston and cylinder assembly 12. To the piston of assembly 12 is attached a movable head that is guided by posts 11 to move up and down. On bed 10 and under the'head 13 are suitably bolted heat riser elementsl6 and 17, respectively, which are of a standard construction and each made of, for example, 2 inches by 1 inch steel plates separated about 5 inches by l by 5 inch steel bars placed about 5 inches center to center and welded to both plates. On each one of the riser elements 16 and 17 is bolted a novel high temperature platen 18.

Referring to FIG. 2, the novel platen 18 is shown as assembled, while in FIG. 3 the platen is shown in an exploded view. The platen 18 has a mounting plate 21 made of, for example, steel, which plate is mounted against one of the riser elements 16 and 17. Next to the mounting plate is disposed a heat sink 22 constructed in a manner that will be described hereinafter. Next to the heat sink 22 is placed a heat insulator ceramic subplate 23 made of a good heat insulating ceramic composition, for example, consisting primarily of alumina and that is about .six inches thick. This is followed by a heat conducting ceramic face plate 24 made of, for example, nitride bonded silicon carbide about two and one half inches thick because silicon carbide has relatively good heat conducting properties for reasons that will be explained hereinafter. Around the heat conducting ceramic face plate 24 is disposed the heat insulating ceramic frame 25 made of a ceramic composition consisting of, for example, alumina and silica whose function is to contain the heat and is, therefore, approximately three inches wide all around the face plate 24.

To hold the novel platen together, heat insulator ceramic subplate 23 has a plurality of transverse or horizontal bores such as bore 31 shown in FIG. 4 preferably extending thereacross from side to side in a shorter dimension. These bores 31 are, for example, one inch in diameter. Communicating with each bore 31 are a plurality of vertical holes 32 extending upward as viewed in FIG. 4 toward the cold side of the platen. Vertical holes 32 are aligned with holes 33, extending through the heat sink 22, and with holes 34 within the mounting plate 21. Standard bolts 36 are disposed in respective aligned holes 32, 33, and 34 and engage respective standard cylindrical barrel nuts 37 within the bores 31. Heat conducting ceramic face plate 24 and the ceramic frame 25 are held in place by a plurality of brackets 41 having a suitably disposed bolt eye 42 at one end and at the other end a dowel 43 made of, for example, stainless steel one quarter inch in diameter that extends through a horizontal hole 44 in frame and into a well 45 in the ceramic face plate 24 as shown. Through the bolt eye 42 are placed bolts 47 that thread into suitable bolt holes 48 in the plate 21. The platens are fitted to the respective heat riser elements 16 and 17 by suitable bolts, not shown, extending through four vertical holes 50 in plate 21 engaging suitable threaded holes (not shown) in the elements 16 and 17.

Since ceramics that can conduct heat such as silicon carbide can also conduct electricity, the ceramic may be elevated in temperature by passing current therethrough, resistably heating the ceramic. However, in large ceramic pieces like face plate 24 that is, for example, 2 A by by 48 inches, the resistivity is not uniform and, if one attempts to pass current therethrough as suggested by the prior art, the current will be conducted along the path of least resistance. Therefore, relatively large platens cannot be uniformly heated in that manner.

Referring to FIG. 4, the ceramic face plate 24 is uniformly heated by the heating rods 51, disposed through horizontal passageways 52 through ceramic face plate 24. These passageways 52 are cylindrical and are disposed midway between the two surfaces of ceramic face plate 24. The rods 51 are made of, for example, silicon carbide because they have the properties of being electrically conducted and do not deteriorate at elevated temperatures in the atmosphere. The rods 51 are, for example, A inch in diameter and 42 inches long. To prevent electrical contact with the ceramic face plate 24, the passageways are made larger, for example, inch in diameter. The rods 51 are prevented from sagging and contacting ceramic face plate 24 by alumina rings 53 placed around the rods 51 as shown in FIG. 4. The rods 51, being longer than the plate is wide, protrudes through suitable openings 54 in the ceramic frame 25 which is, as mentioned above, made of alumina and silica, therefore, no additional electrical insulation is needed between the two. On both ends of the rods 54 are bonded suitable electrical contact tabs 56 as is standard in the art. Current is readily coupled through these tabs 56 to the rods 51. The passageways 52 are placed about 1% inches center to center to thereby provide an even temperature on the exposed face of the ceramic face plate 24.

On opposite side of ceramic subplate 23 from the ceramic plate 24 is the heat sink 22 which is made of two metal sheets 58 and 59 framed in by suitable peripherally disposed bars 60, in a standard manner, to leave an enclosure therebetween through which a cooling fluid, such as water, passes. The water enters through a pipe 61 (FIG. 3) and exits by a pipe 62 disposed in the bars 60. To prevent the sheets 58 and 59 from coming together when force is being applied, suitable spacer blocks 63 are disposed therebetween.

Referring to FIG. 5, one use for the novel platen is shown. The platens 18, as shown in FIGS. 2, 3, and 4 are bolted to the respective heat 'risers l6 and 17. The necessary electrical connections are made to the tabs 56 and the water connections are made to pipes 61 and 62. On a lower platen 18 is placed a retort 71 which includes two flexible stainless steel sheets 72 and 73 welded around their edges to form a vacuum chamber. Therein is disposed the necessary tooling to form a sandwich-panel made of a refractory metal such as columbium. The panel is comprised'of two sheets 74 and 75 and bars 76 disposed therebetween and normal to the sheets 74 and 75. The necessary supports 77, shown schematically, are placed between the sheets 74 and 75 to prevent the bars 76 from buckling under load. Pressure distribution plates 78 and 79 are placed next to the columbium plates 74 and 75, respectively. The supports 77 and pressure plates 78 and 79 are made of a satisfactory refractory metal such as molybdeum which has relatively the same coefficient of heat expansion as columbium. When pressure is applied and the platens are heated, a diffusion bond is formed between the edges of the bars 76 and the respective plates 74 and 75.

While other modifications of this invention and variations of apparatus have not been described, the invention is intended to include all such that may be embraced in the following claims.

What is claimed is:

l. A high temperature platen adapted to be used with a press comprising:

' a face plate of a relatively good heat conducting ceramic having a plurality of bores therein;

a subplate of a relatively good insulating ceramic having parallel planar surfaces and disposed adjacent said face plate;

a heat sink disposed adjacent said subplate;

means for mounting said platen on said press disposed adjacent said heat sink; and

ceramic resistance heater rods disposed in the bores of said face plate supported by insulation supports disposed between each of said rods and the wall of its respective bore.

2. The platen of claim 1 wherein:

said subplate includes at least one first bore disposed parallel to its parallel planar surfaces and at least one second bore communicating with said first bore and opening at one planar surface thereof,

at least one threaded nut disposed in said first bore,

and

at least one bolt extending through said second bore and said heat sink and engaging said nut so that said subplate is fixed to said heat sink.

3. The platen of claim 2 wherein:

a mounting plate is disposed between said heat sink and said press and is adapted to be removably mounted to said press,

a plurality of brackets disposed around said platen and each engaging said mounting plate at one end and said face plate at the other end.

4. The platen of claim 3 wherein:

a heat insulating frame is disposed around said face plate, said frame having means permitting engagement with said brackets.

5. A high temperature platen adapted to be used with a press, said platen comprising:

a metallic mounting plate adapted to be removably mounted to said press,

a heat sink including two metallic sheets separated by peripherally displaced bars to form an enclosure therebetween, suitable spacer blocks disposed within the enclosure to keep the two apart and means for flowing a cooling liquid through said enclosure,

said heat sink being disposed on one side of said mounting plate,

a subplate made of a heat insulation ceramic and having parallel planar surfaces disposed on the other side of said heat sink from said mounting plate,

means for removably joining said mounting plate,

said heat sink and said subplate together,

a face plate having a work contacting surface and including means for heating disposed next to said subplate opposite said heat sink,

a heat insulating frame disposed around said face plate, and

means for fixing said frame and said face plate to said mounting plate.

6. The platen of claim 5 wherein:

said face plate includes a plurality of bores disposed parallel to its work contacting surface,

said means for heating includes electrical resistance heater rods disposed in said bores.

7. The platen of claim 6 wherein:

said face plate is made of a ceramic having relatively good heat conducting characteristics,

said rods are made of a ceramic having relatively good electrical conductivity characteristics,

electrical insulation supports are disposed between said rods and the wall of said bores in said face plate, and

said subplate has opposite parallel planar surfaces and is made of a ceramic having relatively good heat insulation characteristics.

8. The platen of claim 7 wherein said mounting means includes:

said subplate includes at least one first bore disposed parallel to its parallel planar surfaces and at least one second bore communicating with said first bore and opening at one planar surface thereof,

at least one threaded nut disposed in said first bore,

and

at least one bolt extending through said second bore, said heat sink and said mounting plate for engaging said nut so that said subplate is fixed to said heat sink and said mounting plate. 

1. A high temperature platen adapted to be used with a press comprising: a face plate of a relatively good heat conducting ceramic having a plurality of bores therein; a subplate of a relatively good insulating ceramic having parallel planar surfaces and disposed adjacent said face plate; a heat sink disposed adjacent said subplate; means for mounting said platen on said press disposed adjacent said heat sink; and ceramic resistance heater rods disposed in the bores of said face plate supported by insulation supports disposed between each of said rods and the wall of its respective bore.
 2. The platen of claim 1 wherein: said subplate includes at least one first bore disposed parallel to its parallel planar surfaces and at least one second bore communicating with said first bore and opening at one planar surface thereof, at least one threaded nut disposed in said first bore, and at least one bolt extending through said second bore and said heat sink and engaging said nut so that said subplate is fixed to said heat sink.
 3. The platen of claim 2 wherein: a mounting plate is disposed between said heat sink and said press and is adapted to be removably mounted to said press, a plurality of brackets disposed around said platen and each engaging said mounting plate at one end and said face plate at the other end.
 4. The platen of claim 3 wherein: a heat insulating frame is disposed around said face plate, said frame having means permitting engagement with said brackets.
 5. A high temperature platen adapted to be used with a press, said platen comprising: a metallic mounting plate adapted to be removably mounted to said press, a heat sink including two metallic sheets separated by peripherally displaced bars to form an enclosure therebetween, suitable spacer blocks disposed within the enclosure to keep the two apart and means for flowing a cooling liquid through said enclosure, said heat sink being disposed on one side of said mounting plate, a subplate made of a heat insulation ceramic and having parallel planar surfaces disposed on the other side of said heat sink from said mounting plate, means for removably joining said mounting plate, said heat sink and said subplate together, a face plate having a work contacting surface and including means for heating disposed next to said subplate opposite said heat sink, a heat insulating frame disposed around said face plate, and means for fixing said frame and said face plate to said mounting plate.
 6. The platen of claim 5 wherein: said face plate includes a plurality of bores disposed parallel to its work contacting surface, said means for heating includes electrical resistance heater rods disposed in said bores.
 7. The platen of claim 6 wherein: said face plate is made of a ceramic having relatively good heat conducting characteristics, said rods are made of a ceramic having relatively good electrical conductivity characteristics, electrical insulation supports are disposed between said rods and the wall of said bores in said face plate, and said subplate has opposite parallel planar surfaces and is made of a ceramic having relatively good heat insulation characteristics.
 8. The platen of claim 7 wherein said mounting means includes: said subplate includes at least one first bore disposed parallel to its parallel planar surfaces and at least one second bore communicating with said first bore and opening at one planar surface thereof, at least one threaded nut disposed in said first bore, and at least one bolt extending through said second bore, said heat sink and said mounting pLate for engaging said nut so that said subplate is fixed to said heat sink and said mounting plate. 